A heat pump is understood to be any machine which receives thermal energy with the expenditure of mechanical or thermal energy from a reservoir with a lower temperature—for example the environment—, and together with the operating energy as useful heat transfers it to a system which is to be heated with a higher temperature—for instance for the purpose of space heating. This transfer takes place by way of the reversal of a heat and power process known from the prior art, in which thermal energy with a high temperature is received, is partially converted into mechanical effective work and the residual energy at a lower temperature is discharged as waste heat—typically to the environment. The principle of the heat pump can, for example in the case of a conventional refrigerator, also be used for cooling. In the cooling process, the useful energy is the heat received here from the space which is to be cooled, which together with the operating energy is discharged to the environment as waste heat. In the present context, the concept of the heat pump is therefore used in a wider sense and is not intended to comprise merely a heating unit based on the described principle, but equally a corresponding cooling machine.
Heat pumps are generally operated with fluids which vaporize at low pressure under the application of heat and condense again after compacting to a higher pressure under heat dissipation. The pressure is selected here so that the temperatures of the phase transition have a separation from the temperatures of heat source and heat sink which is sufficient for the heat transmission. Depending on the fluid which is used, this pressure lies in various ranges. In addition, sorption heat pumps are known from the prior art which, instead of technical work, use thermal energy as operating energy. Adsorption heat pumps operate here with a solid sorbent, the adsorbent, on which the cooling medium is adsorbed or desorbed. Heat is supplied to this process during the desorption, whereas heat is removed during the adsorption. As the adsorbent generally can not be circulated in a circuit, the process of the heat transmission is operated in a discontinuous manner in this case, by alternating cyclically between adsorption and desorption.
DE 10 2008 060 698 A1 and DE 10 2010 043 539 A1 disclose such a heat pump according to the adsorption principle with a plurality of hollow elements having respectively an adsorption agent, which hollow elements respectively contain a working medium which is transportable between the adsorption agent and a phase change region and are able to be flowed through by a heat-transporting fluid in a fluid circuit which is able to be altered by means of a valve arrangement. The said hollow elements are brought in thermal contact in the region of the adsorption agent through a specific sequence of valve arrangements, which are engaged in a periodic alternation, in order to offer a particularly wide range of application for the heat pump.
The rotary valves used for the cyclic impingement of the sorption modules nevertheless have some fundamental disadvantages. Such a disadvantage lies in the necessary coordination of the rotary valves to the number of sorption modules, which is determined by the type of construction. An output scaling of the installation by simple variation of the connected modules is therefore not possible without the use of a rotary valve which is respectively adapted exactly to the module number. For example, a rotary valve for six connected sorption modules can not be used for the controlling of eight sorption modules.
A further disadvantage lies in that the time for the decoupling of the sensible heat of each module on changing over between the heat carrier circuits of different temperature is coupled to the cycle time of the overall process. For this purpose, exactly calibrated throttles are provided, which define the respective partial flow for the decoupling of the sensible heats and supply into the complementary circuit, which can only be achieved for one cycle time.
This presents itself as a problem in particular in the optimization of the annual use efficiency, which is calculated exclusively from the performance factors (Coefficient of Performance, COP) of partial load states which are operated particularly frequently in the course of the year. Optimal COPs are, however, achieved with distinctly longer cycle times, which then also lengthen the time intervals for the regeneration phases in a detrimental manner.